The present technology relates to a DC/DC (direct-current to direct-current) converter.
An electronic apparatus such as a personal computer, a game dedicated machine, or the like uses a DC/DC converter (switching regulator) for stepping down a direct-current voltage supplied from a battery or an inverter to a voltage level optimum for a load.
FIG. 1 is a circuit diagram showing an example of configuration of a step-down DC/DC converter considered by the present inventors. The DC/DC converter 2r of FIG. 1 is a multi-channel/multi-phase DC/DC converter. The DC/DC converter 2r includes an input line 4, an output line 6, M switching circuits SW1 to SWM, M inductors L1_1 to L1_M, output capacitors Co, a phase controller 116, an oscillator 118, a pulse modulator 120, and a distributing section 122.
The DC/DC converter 2r steps down an input voltage VIN of the input line 4 to a predetermined level, and supplies an output voltage VOUT to a load (not shown) connected to the output line 6. An input capacitor Ci for stabilizing the input voltage VIN is connected to the input line 4. The output capacitors Co for smoothing the output voltage VOUT are connected to the output line 6.
The plurality of switching circuit SW1 to SWM each include a switching transistor M1, a synchronous rectifier transistor M2, and a driver DRV. The ith switching circuit SWi generates a switching voltage VSWi at a point of connection (switching node) between the two transistors M1 and M2 by complementarily switching the two transistors.
The inductors L1_1 to L1_M are provided for each of the switching circuits SW1 to SWM. The ith inductor L1—i is provided between the switching node of the corresponding switching circuit SW1 and the output line 6.
The oscillator 118 generates a periodic signal SOSC having a predetermined frequency. The pulse modulator 120 is for example a pulse width modulator. The pulse modulator 120 generates a pulse signal SPWM in synchronism with the periodic signal SOSC on the basis of a feedback voltage VFB in accordance with the output voltage VOUT. The feedback voltage VFB is for example a voltage obtained by dividing the output voltage VOUT by resistances R1 and R2. The pulse modulator 120 adjusts the duty ratio of the pulse signal SPWM such that the feedback voltage VFB coincides with a predetermined reference voltage VREF. This feedback control stabilizes the output voltage VOUT at a target level VREF×(R1+R2)/R2.
The phase controller 116 sets the number K of driving phases. When M=4, for example, K can be selected from four values of 1, 2, 3, and 4.
The distributing section 122 selects K switching circuits among the M switching circuits SW1 to SWM, and distributes pulse signals SPWM1 to SPWMK with a phase difference of (360/K) degrees to the selected K switching circuits, respectively.
The configuration of the DC/DC converter 2r has been described above. Operation of the DC/DC converter 2r will next be described. In the following, description will be made of a case where M=4 and the number K of driving phases can assume 2, 3, or 4. FIGS. 2A to 2C are waveform charts of switching voltages Vsw1 to Vsw4 when K=2, 3, and 4, respectively.